Defect Generation Research Articles

Multitasking-Effect Ca Ions Triggered Symmetry-Breaking of RuO2 Coordination for Acidic Oxygen Evolution Reaction.

The development of highly active and stable electrocatalysts for the acid oxygen evolution reaction (OER) is both appealing and challenging. The generation of defects is an emerging strategy for improving the water oxidation efficiency. Herein, we introduced multitasking Ca ions to trigger oxygen vacancies in RuO2, resulting in vacancy-rich RuO2 (RuO2-Ov) nanoparticles with enhanced and sustainable OER activity. The oxygen vacancy in RuO2-Ov breaks the symmetry of the RuO6 octahedron, enhancing the d-band center of Ru and reducing the level of 4d-2p hybridization in Ru-O bonds. This effectively optimizes intermediate adsorption and inhibits Ru dissolution. The RuO2-OV catalyst achieves a current density of 10 mA/cm2 with an overpotential of only 198 mV, stabilizing for over 100 h (degradation rate: 0.2 mV/h). Its mass activity is 17.9 times higher than that of commercial RuO2. Our work highlights that multitasking atomic construction defect engineering effectively balances the seesaw relationship between catalytic activity and stability.

Surface Defect Generation on SnO2 Nanoparticles Using High-Energy Ball Milling for H2S Gas Sensor Applications

Hydrogen sulfide (H2S) is a highly toxic and dangerous gas with a flammable and corrosive nature, making the development of reliable gas sensors for its detection vital. This study investigated the enhancement in H2S gas sensing performance of commercial SnO2 powders after high-energy milling. SnO2 powders were subjected to high-energy milling for 30, 60, and 90 min and then were characterized using advanced techniques to evaluate their morphology, chemical composition, and crystallinity. The response of a pristine SnO2 gas sensor, and ones where the SnO2 was milled for 30, 60 and 90 min, were 2.46, 2.27, 3.01, and 1.98, respectively, to 10 ppm H2S at 300°C. Thus, the H2S gas sensing results revealed that the SnO2 powders milled for 60 min exhibited the highest sensing performance. This improvement in H2S sensing performance was attributable to the reduced particle sizes achieved through the high-energy milling process, which increased the surface area and created defects on the surface of the SnO2 particles, thereby enhancing the interaction between the gas molecules and sensor material. The smaller morphological size of the particles and surface defects subsequently promoted the resistance modulation crucial for H2S gas detection. This study demonstrates that high-energy ball milling can effectively boost the gas-sensing features of SnO2 powders. The findings can provide guidance for enhancing the gas-sensing capabilities of other resistive sensors.

Hydride-Induced Reconstruction of Pd Electrode Surfaces: A Combined Computational and Experimental Study.

Designing electrocatalysts with optimal activity and selectivity relies on a thorough understanding of the surface structure under reaction conditions. In this study, experimental and computational approaches are combined to elucidate reconstruction processes on low-index Pd surfaces during H-insertion following proton electroreduction. While electrochemical scanning tunneling microscopy clearly reveals pronounced surface roughening and morphological changes on Pd(111), Pd(110), and Pd(100) surfaces during cyclic voltammetry, a complementary analysis using inductively coupled plasma mass spectrometry excludes Pd dissolution as the primary cause of the observed restructuring. Large-scale molecular dynamics simulations further show that these surface alterations are related to the creation and propagation of structural defects as well as phase transformations that take place during hydride formation.

Stress redistribution and failure of mobile machines frame during propagation of crack-like defects

Stress redistribution and failure of mobile machines frame during propagation of crack-like defects

Epitaxial growth and characterization of gan thin films on 2D MoS2 substrates via plasma-assisted molecular beam epitaxy

Gallium nitride (GaN) is an excellent material for high-performance optoelectronic and power electronic devices due to its superior thermal conductivity and exceptional electron transport properties. However, growing high-quality GaN films is challenging because of lattice mismatch and thermal expansion coefficient differences with conventional substrates like sapphire and silicon, resulting in threading dislocations and structural defects that compromise device performance. This study addresses these issues by utilizing a 2D-MoS₂ buffer layer, which provides an atomically smooth surface and quasi-van der Waals interface to minimize lattice mismatch stress and suppress defect propagation. GaN thin films were grown on MoS₂-deposited c-sapphire substrates using plasma-assisted molecular beam epitaxy (PA-MBE) under optimized conditions. The MoS₂ layer was prepared using a chemical vapor deposition process followed by nitridation. Characterization techniques, including Reflection High-Energy Electron Diffraction, Atomic Force Microscopy, Field Emission Scanning Electron Microscopy, and X-ray Diffraction, confirmed that the GaN films exhibited high crystallinity, phase purity, and preferred c-axis orientation, with minimal structural defects. Surface analysis showed moderate roughness, with a root mean square value of 11.35 nm, attributed to localized growth variations. The MoS₂ buffer layer significantly reduced lattice mismatch-induced stress, as indicated by the absence of secondary phases in XRD analysis and facilitated defect-free epitaxial growth. These findings demonstrate the transformative potential of combining PA-MBE with 2D material buffers to achieve high-quality GaN films. This approach holds promise for optoelectronic applications such as LEDs and laser diodes, as well as high-frequency electronic devices like high-electron-mobility transistors

Deep learning potential model of displacement damage in hafnium oxide ferroelectric films

A model for studying displacement damage in irradiated HfO2 ferroelectric thin films was developed using deep learning and a repulsive table, combining the accuracy of density functional theory with the efficiency of molecular dynamics. This model accurately predicts the properties of various HfO2 phases, such as PO (Pca21), T (P42/nmc), AO (Pbca), and M (P21/c), and describes the atom collision-separation process during irradiation. The displacement threshold energies for the Hf atoms, three-coordinated O atoms, and four-coordinated O atoms are 57.72, 41.93, and 32.89 eV, respectively. The defect formation probabilities (DFPs) for the O primary knock-on atoms (PKAs) and Hf PKAs increase with energy, reaching 1. Below 80.27 eV, the O PKAs are more likely to form point defects than the Hf PKAs. Above this energy, the Hf PKAs have a higher DFP because the O PKAs form replacement loops more easily, inhibiting the generation of point defects. This study provides a comprehensive understanding of defect formation, which is crucial for increasing the reliability of HfO2 ferroelectric devices under irradiation.

Facilitating Cathode Regeneration via Defect‐Driven Prelithiation

AbstractDirect regeneration of electrode materials has been in the spotlight due to its potential resource recovery and environmental benefits, especially for LiNixCoyMnzO2 (NCM) cathode materials. Yet, prior studies have predominantly emphasized innovating regeneration methods, overlooking the intrinsic defects of spent NCM and their effects in the regeneration process. This study proposes a mechanism aimed at facilitating lithiation regeneration by modulating the surface defects of spent NCM. The generation of oxygen defects in degraded NCM intensifies the adsorption of lithium source, effectively reducing the energy barrier for Li+ migration from surface to bulk. Simultaneously, mechanical energy is employed to alter the local thermodynamic state to provide a driving force for lithium migration, allowing it to undergo a prelithiation reaction before roasting. The temperature range in which the phase transition occurs during the roasting process becomes more concentrated. This contributes to increasing opportunities for lithium insertion and accelerates the repair of crystal structure, resulting in favorable properties of regenerated materials. This strategy innovatively exploits the inherent defects of spent NCM, proposes the critical role of synergistically regulating defect kinetic and thermodynamic features in facilitating regeneration, providing a unique perspective for the design of direct NCM regeneration technology.

Unveiling the interactions between preexisting dislocations and displacement cascades in the refractory high-entropy alloy WTaCrV

Refractory high-entropy alloys (RHEAs) represented by WTaCrV are excellent candidates for future nuclear reactor structures. Both the preexisting edge dislocations (EDs) and screw dislocations (SDs) can significantly impact the irradiation performance of RHEAs. To explore the influence of preexisting dislocations on the generation and evolution of irradiation point defects in the RHEA WTaCrV, the interactions between preexisting dislocations (including EDs and SDs) and displacement cascades are studied by molecular dynamics simulations in this work. In addition, the results of the RHEA WTaCrV without preexisting dislocations and of pure W with preexisting dislocations are included for comparison. It is found that the presence of preexisting dislocations leads to a significant increase in the number of remained point defects after the cascades. However, the absorption of vacancies by dislocation cores in the RHEA WTaCrV is more significant than that in the pure W. Therefore, preexisting dislocations can reduce the possibility of void formation and act as sites for recombination of vacancies and interstitials in the subsequent long-term evolution. For the preexisting EDs in the RHEA WTaCrV, the local pinning of EDs, the attraction of vacancies, and the severe lattice distortion jointly cause the bowing out of EDs, which is conductive to accommodate vacancies. For the preexisting SDs, the abundant cross kinks tend to bind vacancies or interstitials, promoting the motion of SDs as well as the annihilation of point defects. In this sense, the preexisting dislocations in the RHEA WTaCrV can significantly enhance the irradiation resistance. The results of this research can provide design guidance for regulating the anti-irradiation performance of RHEAs.

Multifunctional Regulation of Chemical Bath Deposition Based SnO2 for Efficient Perovskite Solar Cells.

SnO2 prepared by chemical bath deposition (CBD) is among the most promising electron transport layers for enabling high efficiency, large area perovskite solar cells (PSCs). However, the uneven surface coverage of SnO2 and the presence of defects in the film and/or at the SnO2/perovskite interface significantly affect the device performance. Herein, a multifunctional molecule of phosphorylcholine chloride (CP) is introduced to modulate the CBD growth of SnO2 and suppress the generation of defects. The agglomeration of SnO2 nanoparticles is hindered due to the electrostatic repulsion effect, leading to the formation of dense and conformal films with improved optical transmittance and electrical conductivity. Moreover, the defects both in SnO2 and at the interface of SnO2/perovskite are successfully passivated and the energy band structure is well regulated, contributing to the suppression of nonradiative recombination and the improvement of electron transport. As a result, a remarkably high power conversion efficiency (PCE) of 24.04% is attained for PSCs processed in air ambient. The unencapsulated devices exhibit improved long-term stability, maintaining over 80% of their initial PCE after storing in air ambient for 1500h or under one-sun illumination for 600h.

Synergetic Optimization via Indium and Rare Metal Yttrium Co-doping in GeTe Results in High Power Factor and Excellent Thermal Performance.

Excess intrinsic Ge vacancies in GeTe materials lead to excessively high hole concentration and high thermal conductivity, producing poor thermoelectric performance. Here, synergistic control and optimization of the thermoelectric transport properties and microstructure of GeTe-based materials were achieved through co-doping with In and rare earth element Y, resulting in a significant enhancement of thermoelectric performance. The Ge0.94In0.03Y0.03Te sample reached a ZTmax of 1.84 at 773 K, representing an increase of around 91% compared to the GeTe matrix. The experimental results indicate that the doping of In optimizes the band structure by introducing resonant levels and increasing the degeneracy of the valence band. Y doping introduces in situ nanoscale secondary phases and lattice distortions due to defect generation, enhancing phonon scattering and significantly reducing the κlat. This work elaborates on how co-doping with In and Y achieves the optimization of the thermoelectric performance of GeTe-based materials. While the electrical transmission characteristics are improved, the thermal conductivity is significantly reduced. For the Ge0.94In0.03Y0.03Te sample, κlat decreased to ∼0.56 W m-1 K-1 at 573 K, resulting in a ZTave of ∼0.99 over the entire temperature range, representing over 140% improvement compared to undoped GeTe. This improvement is significantly higher compared with other works on GeTe and PbTe.

Understanding and Controlling the Formation of Nonradiative Defects in Blue Organic Triplet Emitters

Phosphorescent organic light-emitting devices (PHOLEDs) suffer from destructive molecular processes due to triplet-polaron and triplet-triplet annihilation. These processes are energetically driven and hence are particularly active in decreasing the lifetime of blue PHOLEDs. It has recently been shown that increasing triplet radiative rates via the Purcell effect effectively extends the device operational lifetime by reducing the triplet radiative lifetime, thus decreasing their density and the probability of triplet-annihilation reactions. We provide an analytical framework using Marcus theory to explain the observed, approximately exponential relationship between exciton energy and device lifetime. From transient drift-diffusion dynamics, we show that the Purcell effect reduces the exciton density in the steady state and increases the photoluminescent yield, thereby reducing defect generation rates and extending the device lifetime. We control the radiative rate of excitons in microcavities, thereby connecting the exciton energy and decay rates with the observed device lifetime. The device lifetime is shown to follow a power-law dependence on the Purcell factor (PFm) with m=1.5 to 2.5, dependent on the TTA-to-TPA ratio and photoluminescence quantum yield. From our analysis, a fivefold increase in PF has the potential to extend the blue PHOLED lifetime by up to 2 orders of magnitude, making the blue PHOLED lifetime comparable to that of state-of-the-art green PHOLEDs. Published by the American Physical Society 2024

Hydrothermal-Induced Cationic Vacancies in NiAl Hydroxide for Enhanced Oxygen Evolution Activities through Optimization of eg* Band Broadening.

Nickel-based hydroxides [Ni(OH)2] have attracted significant attention as effective oxygen evolution reaction (OER) catalysts. In recent years, defect engineering has been extensively utilized in Ni(OH)2 modification research. Numerous studies have confirmed that the generation of defects can expose more active sites and regulate electronic states, particularly through the introduction of Al cationic vacancies, which enhance conductivity and thereby improve the catalytic performance. The traditional method for producing cationic vacancies is electrochemical etching. However, this method generates a limited number of vacancies in the catalysts and has the complex etching process. Herein, we found that when NiAl layered double hydroxides were treated using a hydrothermal process at 100 °C in a KOH solution, more Al cationic vacancies were generated. Compared to the traditional method with an Al leaching efficiency of 24%, our proposed method achieved an Al leaching efficiency of 44%. Meanwhile, the electrochemical results showed that the overpotential was reduced by 110 mV at 10 A/g. Further experiments showed that the enhanced OER activities resulting from an increased number of cationic defects lead to structural distortions, which broaden the eg* band, significantly affecting the rate of electron transfer between the electrocatalyst and external circuitry, thereby enhancing the OER activity. This work presents a promising approach to creating cationic defects in Ni(OH)2 for high-performance electrocatalysts.

Thermal defects generation mechanism in laser precision dressing of metal-bonded micro-groove diamond wheel and their influence on grinding silicon wafer

The metal-bonded diamond grinding wheel demonstrates superior grinding capabilities and has been frequently employed to chamfer the edges of semiconductor wafers by meticulously processing micro-groove on the surface. However, the high hardness of diamond wheel poses challenges to the micro-groove processing task. In response to this issue, this paper adopts the deflection laser method to dress the micro-groove of the wheel using a fiber laser. In this paper, the influence of the deflection angle on contour accuracy was studied. The formation mechanism of the recast layer and spatter layer in the laser dressing process was demonstrated, and the influence of surface defects of the wheel on grinding performance was analyzed. The results demonstrated that the laser deflection dressing method had effectively solved the laser energy dispersion problem, improved the micro-groove bevel profile, and arc profile dressing accuracy, the maximum angle, arc radius error values were 0.189°, 0.008 mm. The application of low-power sharpening techniques successfully removed thermal defects, such as hot cracks, recast and spatter layers, which were typically produced during high-power shaping, and this refinement improved the grinding capabilities of the wheel. The dimensions of the silicon wafers after chamfering met the requirements and the surface morphology was found excellent with no cracks.

Mechanical properties and damage plastic model for cement-soil mortar: Laboratory tests and numerical analysis

Cement-soil mortar is a composite material that provides an efficient and cost-effective solution for a wide range of construction applications. This study analyzes the mechanical properties of cement-soil mortar through experimental investigation and explores the application and parameter calibration of the Concrete Damage Plasticity (CDP) model in the finite element simulation of cement-soil mortar. Additionally, an innovative Initial Defect Generation (IDG) method is proposed to enhance the accuracy in simulation of failure mode. The research findings provide a simulation framework that balances simplicity and accuracy for cement-soil mortar. Uniaxial compressive tests are first conducted on cement-soil mortar specimens with water contents ranging from 40 % to 70 %, and cement-to-soil proportions from 30 % to 300 %. Based on the experimental results, the regression relationships correlating unconfined compressive strength (UCS) with elastic modulus, peak strain and stress-strain curves are established. Then, the simplified equations for calculating CDP model parameters from the UCS of cement-soil mortar are further proposed following damage mechanics. A parameter table summarizing the calculation methods for all relevant CDP parameters is provided to streamline the model calibration process. Simulations incorporating the simplified calibration method and IDG method successfully replicated the stress-strain responses and failure modes observed in uniaxial compressive strength tests of cement-soil specimens with varied strength. The results demonstrate the reliability and broad applicability of this simulation framework in predicting the mechanical performance of cement-soil mortar.

Non-linear effects in α-Ga2O3 radiation phenomena

The rhombohedral phase of gallium oxide (α-Ga2O3) is of interest because of its highest bandgap among the rest of the Ga2O3 polymorphs, making it particularly attractive in applications. However, even though the ion beam processing is routinely used in device technology, the understanding of radiation phenomena in α-Ga2O3 is not mature. Here, we study non-linear effects for radiation disorder formation in α-Ga2O3 by varying both the defect generation rate and the density of collision cascades, enabled by comparing monoatomic and cluster ion implants, also applying systematic variations of ion fluxes. In particular, we show that the collision cascade density governs the surface amorphization rates, also affected by the ion flux variations. These trends are explained in terms of the non-linear in-cascade and inter-cascade defect interactions occurring during ballistic and dynamic defect annealing stages. As such, these data reveal new physics of the radiation phenomena in α-Ga2O3 and may be applicable for more predictive ion beam processing of α-Ga2O3-based devices.

Influence of transition metal (Cu) and rare earth metal (Dy) co-doping on spinel zinc ferrite (Cu0.1Dy0.08Zn0.9Fe1.92O4) for improved photocatalytic degradation of industrial effluents

In the present era, design and development of novel, highly stable, easily and magnetically separable, cost effective, and visible light driven catalytic material for the removal of harmful industrial effluents is of great importance. In this context, facile co-precipitation route was adopted for the synthesis of ZnFe2O4 (ZFO), Cu0.1Zn0.9Fe2O4 (CZFO), Dy0.08ZnFe1.92O4 (DZFO), and Cu0.1Dy0.08Zn0.9Fe1.92O4 (CDZFO) and their fabrication was confirmed by XRD, FTIR, SEM, and UV-Visible spectroscopy. The phase analysis of all designed materials exhibits that there is an increment in the crystallite size of co-doped zinc ferrite (CDZFO) i.e. 11.51 nm as compared to ZFO (10.74 nm), CZFO (10.92 nm), and DZFO (11.41 nm). The optical study shows a significant decrease in bandgap of CDZFO i.e. 1.82 eV as compared to DZFO (1.89 eV), CZFO (2.0 eV), and ZFO (2.14 eV). This decrease in optical bandgap and increase in crystallite size of the CDZFO is due to the quantum confinement effect. The photocatalytic efficiency of pure, doped, and co-doped samples was investigated against organic dye (Congo red), pharmaceutical drug (ibuprofen), and colorless organic compound (benzoic acid). The photocatalytic results reveal that CDZFO showed about ∼90 % degradation of Congo red while ZFO, CZFO, and DZFO showed only 59 %, 70 %, and 79 % respectively. Moreover, CDZFO also showed highest photocatalytic removal efficiency against ibuprofen (88 %) and benzoic acid (74 %) out of all other synthesized materials. The remarkable photodegradation ability of CDZFO for all targeted pollutants could be attributed to the generation of crystal defects in its lattice, its small bandgap, and higher absorption in visible region. Furthermore, the recyclability experiment confirmed the stability and reusability of the prepared sample.

The effect of particle toughening layers on the material processibility and forming characteristics of carbon fibre/epoxy prepregs

Introducing toughening materials between laminas is a common approach to enhance the interlaminar toughness of composite materials, thereby improving the crack resistance and damage tolerance. Various physical formats of toughening materials, including particles, veils, and mats, have been introduced. However, the incorporation of solid and separately phased tougheners alters not only the mechanical characteristics of prepregs but also their processability during layup and forming. This alteration can lead to unpredictable forming behaviour and the generation of defects during manufacturing, which has not been extensively investigated.In this work, the effect of interleaving tougheners on the forming and consolidation characteristics of carbon/epoxy prepregs was investigated by measuring the interply friction and bulk factor of prepreg stacks incorporating polyamide particle tougheners of various sizes and shapes at the ply interfaces. Additionally, the feasibility of single diaphragm forming without heating by utilising the low friction characteristic of the particle-coated prepreg surface was explored.

Surface Quality Evaluation of 3D-Printed Carbon-Fiber-Reinforced PETG Polymer During Turning: Experimental Analysis, ANN Modeling and Optimization

This work presents an experimental analysis related to 3D-printed carbon-fiber-reinforced-polymer (CFRP) machining. A polyethylene-terephthalate-glycol (PETG)-based composite, reinforced with 20% carbon fibers, was selected as the test material. The aim of the study was to evaluate the influence of cutting conditions used in light operations on the generated surface quality of the 3D-printed specimens. For this purpose, nine specimens were fabricated and machined under a wide range of cutting parameters, including cutting speed, feed, and depth of cut. The generated surface roughness was measured with a mechanical gauge and the acquired data were used to develop a shallow artificial neural network (ANN) for prediction purposes, showing that a 3-6-1 structure is the best solution. Following this, a genetic algorithm (GA) was utilized to minimize the response, revealing that the optimal combination is 205 m/min speed, 0.0578 mm/rev feed, and 0.523 mm depth of cut, contributing to the fabrication of low friction parts and shafts with a high quality surface, as well as to the reduction of resource waste. A validation study supported the accuracy of the developed model, by exhibiting errors below 10%. Finally, a set of enhanced images were taken to assess the machined surfaces. It was found that 1.50 mm depth of cut is responsible for the generation of defects across the circumference of the specimens. Especially, combined with 150 m/min cutting speed and 0.11 mm/rev feed, more flaws are produced.

Targeted synergistic chemical bonding strategy for Efficient and stable CsPbI3-based perovskite solar cells

Regulating the crystallization process of perovskite film and suppressing iodine-related defects hold significant importance in improving the efficiency and stability of CsPbI3-based perovskite solar cells (PSCs), thereby endowing their more potential for commercial applications. Herein, we introduced 2-Aminoethyl methylsulfone hydrochloride (AMS) into the perovskite precursor solution to establish targeted synergistic chemical bonding involving Lewis acid-base interactions and hydrogen bonds with CsPbI3 perovskite. We emphasize the importance of the DMAPbI3 intermediate phase for the crystal quality of CsPbI3 perovskite, and reveal that diminishing the size of Pb-I framework colloids in precursor solution can facilitate the formation of DMAPbI3 and optimize the crystallization process of CsPbI3 perovskite. Simultaneously, we demonstrate the generation of high valence iodine defects due to the photoinduction, and prove that constructing N-H···I hydrogen bond can effectively passivate the iodine-related defects. Consequently, the CsPbI3-based PSCs display an impressive power conversion efficiency of 19.59% along with markedly improved stability. Our finding presents a feasible strategy for managing perovskite crystallization and mitigating the defects-induced perovskite degradation, thus promoting the commercialization of CsPbI3-based PSCs.

Effect of charge-discharge with higher capacitance performance of Ni-substituted CoFe2O4 magnetic nanoparticles for energy storage

In this work, we synthesized NixCo1-xFe2O4 (0 ≤ x ≤ 0.8) magnetic nanoparticles (MNPs) by using ultrasonication-assisted reverse chemical co-precipitation method. The X-ray diffraction (XRD) patterns confirm the single-phase with mixed spinel structure of the NixCo1-xFe2O4 (0 ≤ x ≤ 0.8) MNPs with the crystallite size range between 12 nm - 17 nm. The molecular dynamics and oleic acid coated Ni-substituted CoFe2O4 magnetic nanoparticles were confirmed by FTIR measurements. The surface composition of NixCo1-xFe2O4 (0 ≤ x ≤ 0.8) MNPs (Ni, Co, Fe and O) and their oxidation states were estimated using X-ray photoelectron spectroscopy. The NixCo1-xFe2O4 (0 ≤ x ≤ 0.8) MNPs are spherical in shape and polycrystalline in nature, confirmed by FESEM and HRTEM measurements. The Ni-substituted CoFe2O4 MNPs with higher zeta potential (ζ) from −24 mV to -41 mV with an increase in Ni concentration, signifies the stable colloidal stability due to the electrostatic repulsion between MNPs. The DC magnetization (M-vs-H) measurements reveal the ferrimagnetic behavior of NixCo1-xFe2O4 (0 ≤ x ≤ 0.8) MNPs, which suppress the saturation magnetization (MS) from 48.6 emu/g to 5.3 emu/g with the enhanced coercivity (HC) from 335 Oe to 1700 Oe with the substitution of Ni2+ ions is in corroboration with electron paramagnetic resonance (EPR) measurements. The enhanced EPR resonance field (Hres = 2335 Oe - 3261 Oe) with the substitution of Ni2+ ions is attributed to the generation of oxygen vacancies and defects, which are predominant in Ni0.8Co0.2Fe2O4, resulting in significantly enhanced electrochemical performance. Therefore, the three-electrode system was utilized to investigate the electrochemical properties of NixCo1-xFe2O4 (0 ≤ x ≤ 0.8) MNPs. The Ni-substituted CoFe2O4 MNPs have demonstrated significantly enhanced capacity retention of 77 % even after 5000 cycles in 1 M H2SO4 electrolyte solution. NixCo1-xFe2O4 (0 ≤ x ≤ 0.8) MNPs exhibit an excellent specific capacity (Cs) of 794.5 F/g at a current density of 1 A/g, signifies the rate of redox reaction at surface electrolyte interface (SEI) is greatly influenced by the surface to volume ratio. Thus, with the enhancement of Ni2+ ions, redox reaction kinetics might become more efficient resulting in the enhanced charge storage capacity.